Occupant size is one of the key metrics in vehicle design to accommodate various sizes and shapes of human beings comfortably and safely. The occupants riding in an automobile are protected by various advanced technology and safety systems. These may include various advanced airbags, seatbelt systems with sensor based pre-tensioning and load limiting capabilities, etc. Safety systems such as airbags and seatbelts are typically optimized for the size of the occupant and his or her seating position. For example, some of these systems can be adjusted electronically or using pyrotechnics to provide optimum protection during a crash based on the size of the occupant.
Current occupant size identification methods include use of weight sensors, seat track position, and visual identifications. Further methods include measuring the radius of webbing on a retractor spool, connecting string potentiometers to the webbing, mounting various types of belt location sensors on the webbing and using cameras, etc. All of these methods require additional parts mounted outside the retractor. Furthermore, these measuring devices add weight, increase costs, and require extra package space to mount them within a vehicle.